Conventionally, image data from digital imagers are processed in some fashion to provide a quality digital representation of the scene being imaged. FIG. 1 illustrates a conventional image process pipeline from the imager to a display system or other system that requires a quality digital representation of the imaged scene.
As illustrated in FIG. 1, an imager 1; comprising a plurality of photosensitive elements commonly referred to as pixels, the physical realization of the pixels being either a plurality of phototransistors or a plurality of photodiodes functioning as light-detecting elements; images a scene and produces a plurality of voltages. In operation a conventional pixel is first reset with a reset voltage that places an electronic charge across the capacitance associated with; e.g., a photodiode. Electronic charge produced by the photodiode when exposed to illumination, causes charge of the diode capacitance to dissipate in proportion to the incident illumination intensity of the scene. At the end of an exposure period, the change in diode capacitance charge is detected and the photodiode is reset. The amount of light detected by the photodiode is computed as the difference between the reset voltage and the voltage corresponding to the final diode capacitance charge.
The voltages generated by the imager 1 are fed to an analog to digital converter 3. The analog to digital converter 3 converts each analog voltage to a digital image data word having a digital value in a range from 0, which conventionally represents no illumination, to some maximum value that represents illumination saturation. If the width of the digital image data word were set to 8-bits, the range of digital values that a digital image data word could realize would be in the range 0 to 255, 0 being no illumination and 255 being saturation.
The digital image data word is then filtered by a filtering subsystem 5. The filtering subsystem 5, in most conventional systems, modifies the digital image data to compensate for any imager characteristic artifacts that were produced by the imager 1 or to compensate the digital image data for defective pixels in the imager 1.
After filtering, the filtered digital image data is processed in an image processing subsystem 7 wherein the digital image data is modified to compensate for dark current, crosstalk, and/or white balance. The filtered digital image data may also be decompressed in the image processing subsystem 7 if the sensor data received from the imager has been compressed. The processed digital image data is further corrected in an image correction subsystem 9. The image correction subsystem 9 may provide gamma correction, color correction, and/or sharpening. The corrected digital image data is then fed to a number of possible subsystems that can further prepare the image data for display, printing, or analysis.
Notwithstanding the various stages of filtering, processing, and correcting in a conventional image data pipeline, the image data may still have various quality issues with respect to noise introduced by the imager or other components along the pipeline. Moreover, utilizing conventional image processing systems, like the one illustrated in FIG. 1, the image data may not be properly compensated for with respect to the lighting conditions used to image the scene or the sensor color responsivity.
It is, therefore, desirable to provide an image-processing pipeline that produces image data of a high quality and that substantially removes any noise or artifacts introduced by the imager or other components along the pipeline. It is also desirable to provide an image processing pipeline that produces image data of a high quality and that substantially compensates the image data with respect to the lighting conditions used to image the scene or the sensor color responsivity.